Formation of Spirulina cultivated field under microgravity - The air-waterinterface profiles in a rotating vessel

From the viewpoint of oxygen supply and recovery in the closed environment such as a space station, the formation possibility of the Spirulina cultiva ted field under microgravity was experimentally investigated. A cylindrical vessel attached with a stainless shaft at the center of the vessel partial ly filled with water was rotated to form low centrifugal force (approximate ly, 10(-1) G at the wall side of the vessel) under microgravity created in the drop tower. When the ratio of the water/vessel volume was set at 81%, i t was found that the air-water interface did not reach the bottom of the ve ssel, although water reached the top-cover. These experimental findings wer e contradicted with the air-water inter face profiles simulated by Leslie e r al., which was considered to be suitable for oxygen supply and recovery s ystem that an air phase was located in the center of the vessel and the air -water interface contacted with both the bottom and the top-cover of the ve ssel. When the stainless shaft and the bottom of the vessel were coated wit h teflon to increase hydrophobicity and the ratio of the water/vessel volum e was set at 60%, it was found that the air-water interface contacted with the bottom and top-cover of the vessel. The water phase, then, rose along a ll side walls and wetted the entire wall in this case. Thus, using the low centrifugal force, we experimentally demonstrated to establish the suitable condition for oxygen supply and recovery system in the closed environment under microgravity.